Nocturnally migrating birds may become disoriented on land and above the sea by artificial lights used for lighting, for example, offshore installations, skyscrapers, or lighthouses. Studies have shown that the degree of disorientation is dependent on the color of the light. In their article “Red light disrupts magnetic orientation of migratory birds” in Nature 364, 525-527 (5 Aug. 1993), Wolfgang Wiltschko, Ursula Munro, Hugh Ford and Roswitha Wiltschko report that red light generally causes disorientation of migrating birds by impairing magnetoreception, whereas the orientation of migrating birds are unaffected in the seasonally appropriate migratory direction in blue light, while green light causes no or only minor disturbance of orientation. However, pure blue or pure green light is not optimal for human vision comfort, and even not acceptable under conditions where safety is concerned, for example, on offshore installations. Furthermore, many (work) environments require at least a limited ability to recognize the color red so as to enable people to recognize safety equipment and signs that are typically red, for example, fire extinguishers or emergency buttons.